Nitrogen-containing tarnish inhibitors in detergent compositions



2,751,420 NITROGENQCONTAINING TARNISH INHIBITORS IN DETERGENT COMPOSITIONS ll-lerhertsmith Sylvester, Leonia, N. ,L, assignor to C01- gate-Palmolive Company, Jersey City, N. 5., a corp-"- ration (if Delaware NoD rawing. Application May 2, 1951,

Serial No. 224,267

3Claims. Cruz- 137 The present invention relates to novel detergent com positions, and more particularly, to detergent compositions having improved anti-tarnishing properties.

Certain detergent compositions have been known for many years and have been Widely accepted since their lime resistance and other valuable properties makethem advantageous for many uses, 'e. -g., dishwashing, launder- Sing, etc. An unexpected ditficulty has been noted in the cleansing of certain metallic surfaces, such as articles made of German silver or having'aGerman silver base, by solutions of such detergent compositions containing certain water-soluble polyphosphate compounds. For example, in the Washing of household utensils such as tableware or "silverware consisting of German silver with such com- }positions, the washed articles may exhibit tarnishing of the metallic surfaces. V e h p Depending upon the nature of the rnaterial, the detergent composition and the conditions employed, the undesirable veffects may "range from a diminution or loss o'f luster of rthe highly polished metalli'csurfac'es to a harsh discoloration or stain, or worse. The tarnish film, if it may be so called, is of such anature that it is 'difiicult toanalyze, even with microscopic or X-ray means. The discoloration tarnishing effects appear to be particularly objectionable in non-soap detergent compositions containing complex 'polyphosphate's, usually in aqueous alkaline solutions 'of such detergent compositions. Such adverse effects repr'e sent a significant problem from the standpoint of consumer appealand in the cleansing and maintenance of such susceptible metals.

It has now been discovered that deter-gent "compositions normally tending in solution to cause tarnishing of German silver and like metals and consisting essentially of watersoluble polyphosphate materials may be improved by incorporation of a minor amount of a non-heterocyclic ammonia derivative having at least one .hydrogen atom attached to a nitrogen atom and being free of all amide 101 th ioamide linkage to inhibit or retard the tarnishing by said detergent compositions in solution. As a preferred embodiment, the present invention relates to detergent compositions consisting essentially of a non-soap watersoluble synthetic detergent, a water-soluble polyphosphate compound, and a minor amount of a non-heterocyclic ammonia derivative selected from the group consisting of ammonium and primary amino compounds as a tarnish inhibitor. The specificity of action of these inhibitors in the relationship set forth is not completely understood at this time. t

h It is a principal feature of the present invention that the detergent composition comprises essentially water-soluble inorganic polyphosphate salts; These salts have the property of inhibiting precipitation of calcium material and the like in aqueous solution and may be considered as derived from orthophosphoric acid or the like by the removal of \yater, though any suitable means of manufacture may be empid ed if desired; These molecularlydehydrated polyphosphate salts may be wholly of par- 2,731,420 latented Jan. 17, 1956 See tiallyneutralized, such as the alkali metal or ammonium salts of tripolyphosphoric, tetraphosphoric, and pyrophosphoricacids. Suitable examples aresodium tripolyphosphate u trgoto "potassium tripolyphosphate, tetra- 5 sodium pyrophosphate, hexasodium hexametaphosphate (Grahams salt), hexasodium ftetraphosphate, etc.

'Indetergent compositions consisting essentially of the indicated polyphosphates either with or without admixture with synthetic'detergents, it will be observed that the tarnishing action manifests itself as a marked discoloration, usually of a yellowish, purplish or blackish shade,

appears to be due priniarilyto some phenomenon induced or existing in the presence of these complex polyphosphatesin the detergent composition. This discoloration which is obviously highly undesirable may be either retarded or inhibited markedly and even substantially eliminated by the addition of a determinable amount of the indicated inhibitors. The mechanism by which these desired results are obtained is not completely understood at thisttime. h h

The novel compositions of the present invention may also contain as an active detersive ingredient a watersoluble non-soap organic synthetic detergent in admixture with the polyphosphates. It is preferred to use the anionic sulphated or sulphonated synthetic detergents (including suitable mixtures thereof.) Included therein are the aliphatic sulphated. or sulphonated detergents, such as the sulphated 'aliphatic'compounds having about 12 to about 26 carbon atoms and, more particularly, the aliphatic acylcontaining compounds having an acyl radical of about 8 to 22 carbon atoms such as the aliphatic carboxylic ester detergents. As suitable examples of aliphatic anionic detergents may be found 'the sulphuric acid esters of polyhydric alcohols incompletely esterified with higher fatty acids, e. "g. coconut oil monoglyceride monosulphate, tallow diglyceride monosulphate; the long chain pure or mixed higher alkyl sulphates, e. g. lauryl sulphate, cetyl sulphate, higher fatty alcohol sulphates derived from reducedcoconut fatty acids; the hydroxy sulphonated higher fatty acid esters, e. g. higher fatty acid esters of 2, 3 dihydroxy propane sulphonic acid; the higher fatty acid esters of low molecular weight alkylol 'sulphonic acids, e, g. olei c ester of isethionic acid; the higher fatty acid ethanolarnide sulphates; the higher fatty acid amides of amino alkyl sulphonic acids, e. g. lauric amide of taurine, and the like. I

It is a feature of this invention that the desired effects are particularly enhanced With the alkyl aryl sulphonate detergents. These aromatic sulphonate detergents are also well known in the art. They may be monoor polynuclear in structure. More particularly, the aromatic nucleus may be derived from benzene, toluene, xylene, phenol, cresol,s,,naphthalcne, etc. The alkyl substituent on the aromatic nucleus may vafy Widely as long as the desired detergent power of such active ingredient is preserved. e, e

More specific examples, of suitable alkyl aromatic sulphonate detergents are the higher alkyl aromatic sulphonates. The higher alkyl substitutent may vary widely. Thus, it may be branched or straight-chained in structure and comprise decyl, dodecyl, keryl, mixed long-chain alkyls from polymeric lower mono-olefins, etc. Preferred examples of this class are the higher alkyl mono-nuclear aryl sulphonates wherein the alkyl groups is about 8 to about 22, and preferably about 12 to about 18 carbon atoms. More particularly, it is preferred to use the higher alkyl benzene sulphonahes wherein the higher alkyl group ayerag'es about 12 to about 16 carbon atoms. For example, propylene maybe polymerizedto the tetram er and condensed with benzene in the presence of a Friedel- Crafts catalyst to yield essentially the dodecyl benzene 3 derivative which is suitable for sulphonation to the desired sulphonate compounds.

These various anionic. detergents are generally used in the form of the water-soluble salts, such as the alkali metal, alkaline earth metal, ammonium, amine and alkylolamine salts. While the sodium, potassium, ammonium and alkylolamine (e. g. mono, di, and triethanolamine) salts are preferred ordinarily, other salts such as the lithium, calcium, and magnesium salts may be used if desired. For general use, it is ordinarily preferred to use the sodium and potassium salts. For certain specialized uses, it may be preferred to select the ammonium and alkylolamine salts in view of their generally greater solubility in aqueous solution.

It is within the scope of the present invention that nonionic detergents may be present in the detergent composition and, if desired, in admixture with other compatible detergents such as suitable anionic sulphated or sulphonated ones described above. These non-ionic agents are also well known in the art and include the polyoxyethylene ethers of alkyl aromatic hydroxy bodies (e. g. the alkylated polyoxyethylene phenols) and the polyoxyethylene ethers of long chain aliphatic alcohols, etc. Long chain derivatives of polyhydroxy compounds such as the appropriate ethers of polyalkylene glycols may also be employed therein.

It has been found that particularly desirable effects are observed with the inhibitors in built synthetic detergent compositions consisting essentially of the indicated synthetic detergents and the polyphosphates. More particularly, it is preferred to use compositions consisting essentially of about to about 50% and usually about to about 40% synthetic detergents, preferably of an anionic sulphated or sulphonated nature, and about 10 to about 80% and usually about to about 60% of these water soluble polyphosphates, preferably tripolyphosphate, the above percentages being by weight of total solids of the detergent compositions. Where the amount of the polyphosphate detersive ingredient is substantial (e. g. at least about 20% and particularly at least about and major with respect to the proportion of organic synthetic detergent, tarnishing eifects are particularly objectionable and a suitable amount of inhibitor should be present therein in order to produce a satisfactory composition.

The tarnish inhibitor is a non-heterocyclic ammonia derivative selected from the class of ammonium and amino compounds having at least one hydrogen atom attached to a nitrogen atom, and being free of an amide or thioamide linkage, i. e., having no structure in the molecule. The term amino compounds as used in the specification and claims refers to compounds possessing a true amino group, e. g. having a basic amino linkage, and is exclusive of amide or thioamide-containing derivatives. Of the ammonium compounds, the ammonium hydroxide and its salts, particularly the inorganic ones, are preferred usually. Specific examples of suitable ammonium compounds are ammonium hydroxide, diammonium phosphate, ammonium nitrate, ammonium sulphate, etc. The suitable amines include both the aliphatic and aromatic primary or secondary amines. The aliphatic amines are preferred, particularly those containing primary amino groups. Among the suitable amines are the monoand polyamines such as the alkylene polyamines, e. g. ethylene diamine, diethylene triamine, triethylene tetramine, etc. The alkylolamines also yield particularly effective results, such as the ethanolamines (e. g. monoethanolamine) hydroxyethyl ethylene diamine, etc. The amino compounds may also contain other inert substituents, such as taurine, methyl taurine, glycine, Z-aminoethylsulphuric acid, etc. It is thus seen that a rather wide variety of tarnish inhibitors is available in accordance with the invention. The preferred inhibitors yielding optimum results are ethylene diamine, hydroxyethyl ethylene diamine, diethylene triamine, triethylene tetramine, and monoethanolamine.

The amount of the indicated tarnish inhibitor in the detergent composition is generally extremely small, usually up to a maximum of a few per cent (e. g. about 5%), and effective to produce the desired improvements in the tarnish inhibition or prevention. Generally, the amount will be less than about 3% by weight of the composition. While greater amounts may be employed if desired it will usually be found that amounts from about /2 to about 5% are satisfactory with commercial detergent compositions with effective results, particularly with built synthetic detergent compositions.

Further conditions indicative of the complexity of the phenomenon involved and the specificity of action of these tarnish inhibitors and the like are the alkalinity of aqueous solutions of the detergent, and the concentration of solids therein. Illustratively, a built detergent composition consisting essentially of 35% sodium higher alkyl benzene sulphonate, 40% sodium tripolyphosphate and the balance essentially sodium sulphate with minor amounts of sodium silicate, carboxymethylcellulose, etc., and having a pH in 0.5% solution of about 911, and usually about 9.5-10, exhibits marked discoloration of German silver within a relatively short time. Such adverse effects are largely eliminated by the addition of a suitable amount of inhibitor. If, however, the pH of the above detergent composi tion without inhibitor is lowered to substantially neutral values, the degree of tarnishing appears to be correspondingly diminished, and even to an extent that the results otherwise may not be objectionable visually. With the above composition and the like, the critical pH value appears to be within the range of about 7.5-8.5, and usually about 8. Above such values for aqueous solutions of the detergent composition, adverse efiects are most marked and the use of the inhibitor yields optimum results.

It has been found moreover that more pronounced tarnishing is encountered using about 0.25% to 1% solids concentrations of the above detergent composition in aqueous solution than result from the use of more concentrated solutions. With the use of a suitable amount of the indicated inhibitors in such aqueous solutions containing 1.5% solids or less, the presence of the inhibitor results in considerably reduced staining on German silver in comparison to controlled articles exposed to detergent solutions of similar strength but in the absence of inhibitor. Furthermore, a 2% or more solution of the above detergent composition without inhibitor does not appear to stain German silver in ordinary use. The reason for such criticality of action is not understood at this time.

The additives of the present invention may be incorporated with the detergent composition at any stage during the manufacture or use by the ultimate consumer, although it is preferred to incorporate them at the time of manufacture of the detergent composition so that the tarnish inhibitor and detergent composition may be sold to the user as a unitary composition. Thus, the additives may be incorporated at any point during the manufacturing process at which subsequent operations will not adversely modify the properties of the detergent compositions. The various ingredients may be dry-mixed or Wetmixed in any suitable manner. A procedure which is convenient, economical and productive of the best results with synthetic detergent compositions is the addition of the inhibitor in the form of an aqueous or alcoholic slurry to an aqueous slurry of the active detersive ingredients with vigorous stirring to form a relatively smooth, uniform and homogeneous paste. Thereafter these compositions may be prepared in the form of solutions, pastes or as dry or partially hydrated solid products, preferably in finely divided condition. Accordingly, the slurry of the detergent composition may be subjected to any suitable drying operation and converted to particle form. The mixture may thus be subjected to conventional spray-drying, roll-drying or drum-drying operations utilizing temperature of above 212 F., depending upon the nature and stability of the inhibitor, to obtain heat-dried homogeneous detersive particles.

It is common to employ various adjuvant materials in detergent compositions. The detergent compositions, particularly the organic synthetic type, may include any of these substances employed by the art in admixture with such detergent compositions, provided the use of any such materials does not completely neutralize or prevent the desired effects. These builders or additives may be inorganic or organic in structure and may be mixed with the active ingredients in any suitable manner and amount. Conventional builders are the various alkali metal phosphates (e. g. trisodium phosphate), the alkali metal silicates, sulphates, carbonates, etc. Suitable organic materials such as sodium carboxymethylcellulose, fatty acid amides, alcohols, esters may also be employed herein.

The following examples are additionally illustrative of the nature of the present invention and it will be understood that the invention is not limited thereto:

A detergent composition is prepared by compounding 35% sodium dodecyl benzene sulphonate, 40% sodium tripolyphosphate, 3% sodium N silicate, 0.8% carboxymethylcellulose and 0.06% optical bleach (Blancophor MVI) and the balance sodium sulphate.

An aqueous 1% solution of the foregoing detergent composition stains German silver as indicated by the following simple test which involves the immersion of metal strips in the detergent solution to be tested under selected time and temperature conditions: Approximately milliliters of the 1% detergent solution is poured into a milliliter beaker and placed on a hot water bath until a temperature of about 50 C. is reached. German silver strips (Whitehead metal, 14 BS A hard, approximately 18% nickel, 65% copper, 17% zinc) are cut to x 2" size. Each strip is abraded using wet #320 A Behr-Manning Durite abrasive paper. The strips are thoroughly rinsed in running tap water using a toothbrush, then dipped in denatured ethyl alcohol and airdried on a clean towel. The strips are then half immersed in the above-mentioned 1% detergent solution and after 30 minutes at 50 C. are removed and patted dry with a clean towel. This procedure produces a dark stain on the surface of the German silver.

Similar results are obtained using 0.25% solution of the above detergent composition also.

The addition of minor amounts of the following compounds to the above detergent composition inhibits tarnishing of the German silver in the above tests: ammonium hydroxide, diammonium phosphate, ammonium nitrate, ammonium sulphate, ethylene diamine, hydroxyethyl ethylene diamine, diethylene triamine, triethylene tetramine, taurine, methyl taurine, glycine, monoethanolamine and Z-amino-ethylsulphuric acid. Optimum efiects are obtained with the amino compounds. For each specific composition, the optimum amount of inhibitor may be readily ascertained. For example, in 1% total solids solutions of the above detergent composition, the addition or" hydroxyethyl ethylene diamine or ethylene diamine in 0.75% of total solids prevents staining of the German silver in the relationship set forth whereas diethylene triamine in about 2% of total solids should be used for stain prevention, though tarnish inhibition is obtained with lesser amounts also.

Example II A detergent composition is prepared by forming about a 57% solids slurry containing on a solids basisabout sodium dodecyl benzene sulphonate (derived from a propylene tetramer), about 40% sodium tripo'lyphosphate; 15% sodium sulphate, and the remainder minor amounts of sodium chloride, sodium hydroxide, sodium carboxymethylcellulose, etc. This slurry is agitated at about F. in a conventional soap crutcher to form a relatively homogeneous mixture. Hydroxyethyl ethylene diamine in an amount of 3% of total solids of the slurry is added in the form of an aqueous slurry to the detergent slurry which is further agitated to form a uniform mixture. The slurry is then subjected to spray-drying with heated air at a temperature of about 350 F. with a resultant moisture loss of about 40%. The resultant composition is recovered in the form of beads and has a pH of about 9.5-9.7 in 0.5% aqueous solution. This composition gives eilective inhibition of tarnishing of German silver also.

Example III A detergent composition is prepared by the procedure of Example II with the modification that the organic detergent is sodium lauryl sulphate in 20% concentration of solids, and a proportionately increased amount of sodium sulphate. The presence of 3% ethylene diamine gives similarly satisfactory results. I

Other formulations which are productive of desired results are:

While the invention has been described in conjunction:

with its effect in substantially completely preventing the tarnishing of articles of German silver alloy, it is to understood that it is also useful in conjunction with detergent compositions which are to be applied to other metals and alloys subject to tarnishing by such compositions. However, it is particularly efiective with detergent compositions intended for use with the class of predominantly copper base alloys of which German silver and brass are well known members.

The term consisting essentially of as used in the definition of the ingredier s present in the composition claimed is intended to exclude the presence of other materials in such amounts as to interfere substantially with the properties and characteristics possessed by the composition set forth but to permit the presence of other materials in such amounts as not substantially to affect said properties and characteristics adversely.

Although the present invention has been described with reference to particular embodiments and examples, it will be apparent to those skilled in the art that variations and modifications of this invention can be made and that equivalents can be substituted therefore without departing from the principles and true spirit of the invention.

Having described the invention what is desired to be secured by Letters Patent is:

l. A detergent composition tending in normal use to cause tarnishing of a copper base alloy in water solution consisting essentially of a water-soluble polyphosphate 7 salt selected from the group consisting of tripolyphosphates and pyrophosphates, and having present therein a minor amount of a nitrogen-containing compound selected from the group consisting of ammonium hydroxide,

diammonium phosphate, ammonium nitrate, ammonium sulphate, ethylene diamine, hydroxyethyl ethylene di amine, diethylene triamine, triethylene tetramine, taurine, methyl taurine, glycine, monoethanolarnine, and 2-aminoethylsulphuric acid suflicient to inhibit said tarnishing.

2. A built detergent composition normally tending to cause tarnishing of a copper base alloy in water solution consisting essentially of about 10 to about 50% by weight of a synthetic detergent selected from the group consisting of Water-soluble organic sulphated and sulphonated synthetic detergents and about 10 to about 80% by weight of a Water-soluble polyphosphate salt selected from the group consisting of tripolyphosphates and pyrophosphates, and having incorporated therein about /2 to about 5% by weight of a nitrogen-containing compound selected from the group consisting of ammonium hydroxide, diarnrnoniurn phosphate, ammonium nitrate, ammonium sulphate, ethylene diamine, hydroxyethyl ethylene diamine, dietnylene triamine, triethylene tetramine, taurine, methyl taurine, glycine, monoet'nanolamine, and Z-aminoethylsulphuric acid to inhibit said tarnishing.

3. A built detergent composition normally tending to cause tarnishing of a copper base alloy in water solution consisting essentially of about to about 50% by weight of a Water-soluble higher alkyl aryl sulphonate detergent andabout 10 to about by weight of a water-soluble polyphosphate salt selected from the group consisting of tripolyphosphates and pyrophosphates, and having incorporated therein about /2 to about 5% by weight of a nitrogen-containing compound selected from the group consisting of ammonium hydroxide, diammonium phosphate, ammonium nitrate, ammonium sulphate, ethylene diamine, hydroxethyl ethylene diamine, diethylene triamine, triethylene tetramine, taurine, methyl taurine, glycine, inonoethanolarnine, and Z-amino-ethylsulphuric acid to inhibit said tarnishing.

References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES Industrial and Engineering Chemistry, vol. 28, No. 2, Organic Inhibitors of Corrosion, February 1936, by Mann, Lauer and Hultin, pgs. 159-163. 

1. A DETERGENT COMPOSITION TENDING IN NORMAL USE TO CAUSE TARNISHING OF A COPPER BASE ALLOY IN WATER SOLUTION CONSISTING ESSENTIALLY OF A WATER-SOLUBLE POLYPHOSPHATE SALT SELECTED FROM THE GROUP CONSISTING OF TRIPOLYPHOSPHATES AND PYROPHOSPHATES, AND HAVING PRESENT THEREIN A MINOR AMOUNT OF A NITROGEN-CONTAINING COMPOUND SELECTED FROM THE GROUP CONSISTING OF AMMONIUM HYDROXIDE, DIAMMONIUM PHOSPHATE, AMMONIUM NITRATE, AMMONIUM SULPHATE, ETHYLENE DIAMINE, HYDROXYLENE ETHYLENE DIAMINE, DIETHYLENE TRIAMINE, TRIETHYLENE TETRAMINE, TAURINE, METHYL TAURINE, GLYCINE, MONOETHANOLAMINE, AND 2-AMINOETHYLSULPHURIC ACID SUFFICIENT TO INHIBIT SAID TARNISHING. 